Who is Kim Yong-nam?

The 90-year-old Kim Yong-nam has seen the rule of all three North Korean leaders in his career.

He is the ceremonial head of state who receives credentials from foreign diplomats in Pyongyang. As such, he is usually responsible for sending condolences or congratulatory messages to foreign leaders.

He has been the president of North Korea's rubber-stamp parliament, the Supreme People's Assembly, since 1998.

Unlike the current leader Kim Jong-un, Kim Yong-nam has travelled abroad on official visits. In August 2017, he travelled to Iran to attend President Hassan Rouhani's inauguration ceremony for his second term in office.

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Image captionThe two Koreas, still technically at war, are separated by a Demilitarised Zone (DMZ)

He also attended the opening ceremony of the Winter Olympic Games in Sochi, Russia in 2014.

Mr Kim is said to be a loyal follower of the top leadership. "As Kim is known to be acting and speaking under the country's guidance, he makes no mistakes. That's why he could keep his high-level post in a country where political purges are common," South Korea's Yonhap news agency quoted one North Korean defector as saying.

What is the significance of his visit?

An unnamed official from the South's presidential Blue House told the BBC that they believed Mr Kim's visit reflected a willingness on the part of North Korea to improve inter-Korean relations, and demonstrated the North's sincerity.

Seoul has said it will seek high-level talks with the North Korean delegation during the visit, Yonhap reported.

Mr Kim's attendance at the opening ceremony will also put him in the company of US Vice President Mike Pence, at a point of high tension with Washington over the North's nuclear ambitions.

Mr Warmbier and his wife, Cindy, were guests of US President Donald Trump at last week's State of the Union address.

How has the North been involved in the Games so far?

North Korea on Monday proposed sending an art troupe to the Games by ferry, a move that would require an exemption from bilateral sanctions.

Pyongyang proposed that its delegation use the Mangyongbong 92, a ferry that usually operates between North Korea and Russia, for transportation and as accommodation for the group, according to the South's unification ministry.

All North Korean ships have been banned from entering South Korean ports since 2010.

"We're seeking to apply an exemption... to support a successful hosting of the Olympics," South Korean ministry spokesman Baik Tae-hyun told a press conference.

On Sunday, the united Korean women's ice hockey team played its first match, but lost the friendly against Sweden 1-3.

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Image captionThe newly formed joint Korean ice hockey team did not prevail in the friendly against Sweden

Sunday's outing was the first and only practice match for the newly minted Korean squad.

As well as the ice hockey players, North Korean athletes will compete in skiing and figure skating events. It is also sending hundreds of delegates, cheerleaders and performers.

What are relations like between North and South Korea?

North Korea currently faces growing international pressure and sanctions over its nuclear and missile programmes after it conducted a series of missile tests designed to demonstrate its nuclear capability.

North Korea's participation in the Olympics, which run from 9 to 25 February, was an unexpected warming of ties.